Luminescent tube system and apparatus



March 2, 1948. J. H. BRIDGES 2,436,951

LUMINESCENT TUBE .SYSTEM AND APPARATUS Filed Aug. 12, 1943 2Sheets-Sheet 1 M r 1948. J. H. BRIDGES LUMINESCENT TUBE SYSTEM ANDAPPARATUS Filed Aug. 12, 1943 I 2 Sheets-Sheet 2 wue/wtom Patented Mar.2, 1948 LUMINESCEN'I TUBE SYSTEM AND APPARATUS I John Herold Bridges,Paterson, N. J., assignor, by mesne assignments, to National InventionsCorporation, a corporation of New Jersey Application August 12, 1943,Serial No. 498,344

3 Claims. (Cl. 315-257) My application is a continuation in part of mycopending application Serial No. 469,365 of December 17, 1942, entitledLuminescent tube system and apparatus, which issued January 7, 1947, asUnited States Patent No. 2,413,681, and the invention relates in generalto electric lighting systems and more especially concerns luminescenttube systems of illumination and apparatus therein.

The object of my invention is the provision of a safe, reliable andhighly practical gaseous electric discharge tube lighting systemincluding a transformer source of electrical energy and a plurality oftubes, which system is characterized .by. thoroughly satisfactorydistribution of current to the tubes, by prompt and substantiallysimultaneous energization of the tubes, in which there is displayed'butlittle stroboscopic effect, and which during operation has anexceedingly good power factor.

Another object of my invention is the provision of a gaseous electricdischarge tube lighting'system including a single-transformer source ofelectrical supply, which system is especially adapted for operatingfourup to as many as ten or more included light tubes, which achieves highlyeffective control over the tube-energizing current, and which is capableof continued operation in a safe and efficient manner despite failure ofone or more of the plurality of included tubes.

Other objects will in part be obvious and in part pointed outhereinafter in connection with the following description taken in thelight of the accompanying drawing.

In the accompanying drawing Figure 1 represents a gaseous electricdischarge tube lighting system including certain features of myinvention, while Figure 2 is a diagram of the circuit employed in Figure1 and additionally illustrates an advantageous grouping of tubes, and;

Figure 3 depicts a modified form of system in accordance with myinvention.

As conducive to a clearer understanding of certain features of myinvention, it may be noted at this point that gaseous electric dischargetube lighting systems are today in wide acceptance in various fields ofillumination where incandescent lighting systems formerly were employed.There are numerous advantages which more than justify the employment ofsuch lighting systems, among these being characteristically low power.consumption, coolness of operation, simplicity, sturdiness, improveddissemination of light, and

wide choice in the physical form of tube or tubes employed. A number ofdifierent physical dispositions or arrangements, moreover are possiblein obtaining desiredlighting effects as in factories, stores, andprivate homesiand the use of a variety of fillings such as fluorescentsalts on phosphorus as active ingredients of the tubes enables theprovision of a number of different colors of light.

Although, as pointed out, there has been wide acceptance of gaseouselectric discharge tube lighting, many of the systems present featureswhich for practical reasons are not wholly desirable: Certain of thesystems essentially operate at low voltages and the tubes requirepreheating before initial starting is successfully achieved. Thesesystems usually include a heater circuit and switchover mechanism which,as appurtenances, represent items of expense and a source of possibletrouble in operation. A further objection exists in that the tubesflicker during the preheating period and considerable delay occursbefore steady operation is achieved. Hot cathode tube systems also arefound to be unstable in operation at low temperatures, such as undertemperature conditions frequently encountered in outdoor use.

In certain heretofore known gaseous electric 'discharge tube systems ofthe multi-tube type.

failure of one or more of the included tubes disrupts further operationuntil full and proper replacement of the worn out tubes is made. Thislatter objection is notable particularly in lighting systems whichinclude a single transformer source of power and a plurality of tubesconnected in series with each other and with the source of power. Suchsystems also require an increase in operating potential where thenumber, size, or length of tubes is increased. On the other hand anupper limit on voltages is imposed by the fire underwriters and thus thenumber of tubes employed as well as the dimensions thereof are sharplycurtailed.

There too, are multi-tube systems wherein the tubes are connected inparallel across a source, of

electrical supply. In these systems lower operating potentials are madepossible than should series connection of tubes be employed. There is,however, a tendency in such systems for an included tube of low startingpotential or of high conductance to draw such a large part of the loadcurrent available that other included tubes either fail to start, orwhen they do start,'draw such low currents that the current densitiesare wholof the transformer.

step-up transformer portion ll flanked on opposite sides byC-shapedstepped-up output voltage.

1y insufficient to produce the desired brilliant glow.

Still another objectionable feature, commonly termed stroboscopiceffect, is encountered in gaseous electric discharge tube lighting.Stroboscopic effect is a rapid, pulsating effect of the light emittedand gives the impression of unsteady illumination. It is quite tiring tothe eyes, very discomforting, and in all is wholly undesirable.

One of the outstanding objects of my invention, accordingly, is theprovision of a system of;

illumination including a plurality of gaseous electric discharge tubesand a single transformer source of electrical supply, in which systemcontinuous operation of the tubes is not disrupted by failure of one orseveral of the tubes, in which all tubes promptly reach substantiallymomentary flow of primary current through full conductance andbrilliance and give a stable quality of illumination in and afterstarting, and in which a maximum length of tubing is safely andeificiently operated.

Referring now to the general practice of my invention, I provide anelectrical illuminating system which comprises a step-up transformer,

and a plurality of gaseous electric discharge tubes, advantageouslyeight to ten or more, or

even as few as four tubes individually connected in parallel circuitswith a single output source Each tube circuit includes an inductivereactance, and a gaseous electric discharge tube connected in series..One or more of the tube circuits, such as alternate circuitsadditionally include a condenser connected in series with the tube andinductive reactance. The

inductive reactances preferably are of such type as is more fullypointed out hereinafter.

As illustrative of the practice of my invention in Figure 1 of thedrawing there is shown an electric lighting system comprising ashell-type it having an inner core outer core portions l2 and i3. Thetransformer core ismade of paramagnetic material such as of laminatediron. The inner portion of the core preferably has a cross-sectionalarea substantially twice as large as either of the outer core portions.

In assembled condition the transformer core provides two main magneticcircuits on flux paths mutually including inner core portion l l andrespectively including outer core portions i2 and pl'y leads it and iiextend from an alternating current source of electrical supply it,conveniently of 110 or 220 volt rating, to opposite ends of thetransformer primary coil. A secondary coil [5 also disposed about innercore portion ii adjacent the primary coil preferably is wound of smallgauge wire and possesses such number of turns as to have induced thereina desired At times I mount the primary and secondary coils on thetransformer core in superimposed relationship so as '=to gain maximumadvantage of compactness and savings in materials.

While it is within the province of my invention to employ thetransformer it as an ordinary transformer with the primary and secondarydrawing. primary winding to the right along inner core winding is fromleft to right in Figure 1 of the The flux induced courses from theportion 5-! linking secondary coil l5 and returning through outer coreportions l2 and l3 to netically and-an .electromotive force of oppositedirection to that resulting from the first half cycle of primary currentbuilds up .across th transformer secondary winding.

In .the illustrative embodiment of my invention shown in Figure 1, Iemploy some eight to ten or'more, or asfew as four fluorescent gasdischarge tubes; such astubes Tl, T2, T3, T t, etc; connected inparallel across the autotransformer windings of transformer I0..Oneofthe parallel tube circuits conveniently is traced from therighthand side of secondary coil it over lead 22 to terminalfis; thenceover leads Z5 and 26, through tube Ti; along lead 21, winding WI of.reactor'Ptl, and lead 28; over lead 2| to terminal 28; and thence alonglead It, across coil l4, lead it and coil I5 back to the point .ofbeginning.

A secondtube circuit is traced beginning at the righthand sideofsecondarycoil it over lead 22 to terminal 2%; lead 24, condenser C andlead 2cm tube T2, through tube T2, over lead 3i], and across winding W2ofreactor R2; over leads 3| and .2! to terminal Zil; andthence alonglead It, across coil is, lead it, and con 15 back tothe point ofbeginning.

Tube T3 is energized ina circuit traced from the righthand side of coil.lfiover lead 22 to terminal .23; thence over leads 25 and-32, throughtube T3; across lead 33, winding W3 of reactor R3, and leadtii alonglead H to terminal-2B; and across lead vi 6, coil M, lead it and coillE-back to the point of beginning.

Another tube circuit; beginning at the righthand end of coil it, extendsover lead 22, through terminal 23 across lead Z Rcondenser-C, and leadtdto tube T l; thence across tube Ti, lead 36 and winding Wd of reactorR4; along leads -3'| and 2i to terminal '29; and over lead it throughcoil it, lead l9, and coil backto the point of beginning.

Still other serially-connected tubes and reactors may be connectedacross leads 2*] and24 so as to form parallel condensive circuits withthe transformer output'winding, and/or in parallel across leads -2I and25-so as not to include-the condenser C. The tubes of'the entire systemprovided advantageously are grouped or banked such as in pairs ofadjacent or contiguous tubes with one tube only of each pair being in acondensive circuit. Other groupings may be used in which at least onetube in condensive circuit is present, even to the extent of all thetubes of the system being in one bank. Each tube circuit may be closedby a separate switch (not shown) or each bank may be controlled througha separate switch, as pointed out more particularly hereinafter withrespect to the embodiment illustrated in Figure 3.

Where the tubes of the entire system form but one bank, I find advantagein placing alternate tubes in condensive circuits and controlling pairsof adjacent tubes with corresponding switches.

Through the use of a reactor in each of the tube circuits, any tendencyfor one circuit to draw such high currents that the current density inthe remaining circuits is insufficient to produce light at fullbrilliance, is substantially dispelled.

The additional use of a condenser in several of the tube circuits lendsan improved power factor to the entire lighting sytem. Tube in thecondensive circuits, moreover, operate in out of phase relationship withthe tubes in the remaining circuits so as to maintain stroboscopiceffect of light emitted from the system as a whole at a minimum.

The lighting system is highly efficient in operation and has particularutility where some eight or ten or more gaseous electric dischargetubes, or even as few as four of such tubes, of substantial length, areto be energized. The tubes employed are found to have long life due atleast partially to the excellent control over energizing currentmaintained in the system. With an increased number of tubes in thesystem, initial installation costs are readily justified, especiallywhen account is given tothe cost of installing and maintaining a likenumber of tubes in accordance with the prior art. By operating onincreased number of tubes with a single transformer, as for example, upto 70 inches or more of 25 millimeter tubing, core losses in the systemdecrease, and operational efiiciency increases all the more. Thecharacteristic reduction in stroboscopic effect achieved is enjoyed atfull maximum by grouping the tubes so as to obtain blended light fromthe tubes operating in different phase relationship. One advantageousgrouping of tubes is shown diagrammatically in Figure 2 of the drawingwhere paired tubes in adjacent side by side relationship are connectedas in Figure 1 for out of phase operation.

I prefer to use reactors in my lighting system which display little, ifany, current controlling action when no-load conditions prevail, butwhich instantly interpose high reactances when the tube loads areenergized and high currents begin to 110W. 1

A reactor, illustrative of the type just mentioned, is indicatedgenerally in Figure 1 by inference character RI. The embodiment shownincludes a shell-type core comprising a longitudinal inner core portion38 having a reactor winding WI thereon and terminating at one end inoppositely extending transverse portions El, E2. Outercore portions 39and 40 extend from the other end of inner core portion 38 aroundwindin'g WI to vpointsjust short of the ends of extensions El, E2,respectively. The outer core portions thus form magnetic paths throughand around the winding WI, which paths respectively ir clude air-gapsGI, G2, of calibrated high,-

reluctance. I prefer to make core portions 33 and of like cross-sectionand the inner core and equal calibration of air-gaps so as to obtainbalanced magnetic conditions in the several magnetic paths of thereactor. 7

Similarly, reactors R2, R3 and R4 comprise inner core portions 38a, 38band 380, respectively, and corresponding laterally extending'endportions E3, E4; E5, E6; and E1, E8. Reactor windings W2, W3, W4 aremounted on respective inner core portions of the reactors. Outer coreportions 39a, 40a; 39b, 42b; 39c, 40c extending from opposite sides ofthe lefthand ends of the inner core portions, form air-gaps G3, G4; G5,G6, G1, G8 of calibrated reluctance with the laterally extending endportions. I v

In the present embodiment the reactors RIR4 are designed for the same orsimilar tube loads, and one substantially alike in construction. It willbe understood, however, that the reactors may possess-different currentlimiting qualities depending, for example, upon the tube loads to beenergized in-the individual parallel circuits.

The reactors also may to good advantage be of the core-type havingsingle magnetic circuits interrupted by an included air-gap ofcalibrated reluctance. I r When the primary circuit of transformer Ill,including alternating current source of supply I8, lead I6, primarywinding I4 and lead I1, is closed by means of a suitable switch (notshown) an induced voltage is impressed across the transformer outputterminals 20, 23. This voltage rises and falls at the same rate as doesthe curage tending to oppose the provision of the included air-gapsGI-G8 in the reactorcores the decrease in secondary voltage could reachimportant values and could appreciably retard the initial energizationof the tubes. It is to nullify the effect of the self-induced voltagethat th air-gaps GIG8 are provided. The tubes thus are energizedreadily, and high current tends to flow through the system while thetubes remain energized. As soon as this high current fiow is establishedthe reactor coils WI, W2, W3 and W4, however, the conditions in themagnetic circuits of the corresponding reactor cores undergo materialchange. A high flux is set up in the magnetic core circuits, this fluxcrossing air-gaps GIG8 in considerable quantity. A voltage,proportionate to the increased current, is induced in coils WI-W4 tooppose further increase in current through the coils and to limitcurrent flow through the tubes TIT4.

It will, therefore, be seen that the reactors not only permitsubstantially full terminal voltage to be impressed across thecorresponding tube loads at the time of starting, but seem to counteractthe tendency for increase in current flow due to negative resistancecharacteristics of the tube loads or due .to short-circuiting. Theair-gaps in the reactor magnetic circuits, I being of such calibratedreluctance as to prevent a substantial amountof no-load flux frompassing thereacross and yet not being of such 7 high reluctance as toprevent an appreciable amount of flux from crossing while the tubes areenergized, are instr mental in maintaining the tube-energizing currentwithin safe and properly controlled limits without impairment of therapid starting characteristics of the tubes.

In Figure 3 of the drawing a somewhat modified lighting system inaccordance with any invention is illustrated. The system is particularlyuseful where a plurality of light sources controlled by separateswitches are needed asin auditorium or stage li hting or in illuminatina number of rooms of a building. A.v step-up transformer id, such asautotransformer having a primary windin 45 and a s condary W n ingincluding coilsq45 and 46, is employed for energizing some eight to tenor more or even as few as four gaseous electric discharge tubes,illustratively tubes It-T10, connected in parallel with the transformersecondary winding. The tubes preferably are arranged in remotely spacedor contiguous banks, each bank comprising two or more tubes, such astubes T5'I?t, Tl-T8 and T9Tit. At least one tube of each bank, as one oftubes T5, T8 and T! U, is provided with an energizing circuit whichincludes condenser and reactor means; and at least one other tube, asone of tubes T5, T1, and T9 is controlled by reactor means without theaid of a condenser. The tubes in each bank advantageously are groupedtogether as in side by side relationship illustratively in a fixturehaving a. suitable reflector, and are controlled by switch means, asforexample one of the switches, 52 or 5t, independently of tubes in theother banks.

In the embodimental system illustrated in Figure 3, a secondary circuitmay be traced from the righthand side of coil it over leads 61 and 48including switch 45a; lead 49 through reactor R5, lead lsa, tube T5 andleads 5|, 44

to junction 13, and thence along lead 43 through :autotransformer coils5 and 45 back to the point of beginning. A parallel circuit is tracedfrom the righthand side of coil 46 across leads 4'! and it includingswitch 48a, lead 50}, reactor R6 lead 56a, through tube T55 and overlead tub, through condenser cc, leads 560, El and l i to junction 33,and along lead 4| and through coils 45 and it back to the point ofbeginning.

Likewise, parallel circuits are closed across the transformer outputline 44, 41 through lead 52 including switch 52a, first along lead 53,,through reactor Rl, lead 53a, across tube T1 and through lead 532) andlead 55; and, secondly, along lead 5% through condenser 08 and acrossleads 56c and 55.

Similarly, two other parallel circuits are closed across the transformeroutput leads 54, 41, first through lead 56, including switch 56a, acrosslead ii"! and reactor R3, thence over lead 51a and through tube T9, andover leads 5??) and 59; and, secondly, by way of lead 55 includingswitch 56a, lead 58 and reactor RIB, thence across lead 53a and tubeTH], along lead 581) through condenser Cid, and leads 58c .and 59,

respectively.

While the tubes in the several parallel circuits may be energized fromthe transformer secondary winding through individual switches in eachenergizing circuit, particular advantage is gained by energizing thetubes in banks including out of phase tubes through a switchcorresponding to each bank as a whole. Thus when a particular switch isclosed, out of phase operation, is insured and light emitted from theemploy in my li hting syst ms prefer bly ar cold-cathode tubes such ashot-cathode tubes adapted for cold-cathode operation. In this connectionit, should be noted that ordinary hot-cathode tubes are readilyavailable on the market, while at this stage of the art standardCold-cathode tubes are available only on special order. I, therefore,find advantage in shunting the terminals of hot-cathode tubes so as toadapt the tubes for cold-cathode operation. So employed, the tubesdisplay long life and throughly satisfactory light-emissive qualities. Ialso prefer to employ tubes lined with a fluorescent coating or phosphorand filled with a gas such as neon, argon, helium, or the like, with orwithout mercury vapor.

In my lighting system the particular parallel network distributes higheroperating voltages .limits permitted by the fire underwriters forautotransfoimer equipment, a maximum length of tubing is quitesuccessfully energized.

1 Thus it will be seen that with my invention there is provided .asystem of illumination in which the objects hereinbeiore noted, together"with many thoroughly practical advantages, are

successfully achieved. It will be seen that a single transformer outputsource is used in supplying energizing current to a plurality of gaseouselectric discharge tubes in several parallel circuits, and that thevoltage in the several circuits is not only high but of substantiallyuniform value.

It will further be seen that the particular chokecondehser principlesemployed lend to prompt energization of the tubes, at steady characterof illumination substantially free of stroboscopic effect where thetubes are closely grouped as hereinbefore described, and a highlysatisfactory power factor; and that the system is adapted for operatinga maximum length of included tubing and capable of safe, continuedoperation despite the failure of one. or more of the several tubes.

As many possible embodiments may be made of my invention -and'as manychanges may be made in the embodiments hereinbeflore set forth, itwillbe understo-od'that all matter described herein or shown in theaccompanying drawing is to be interpreted as illustrative, and not in alimiting sense.

I claim:

i. A gaseous electric discharge tube lighting system, comprisin 7 incombination, a transformer; at least four gaseous electric dischargetubes; a connection from one side of said transformer to the one ends ofsaid tubes; two connections from the other side of said transformer, onebeing connected to the other ends of one half of said number :of tubesand the other being connected to the other ends of the other one half ofsaid number of tubes; current-limiting self-inductances corresponding innumber to said number of tubes, each of said inductances having amagnetic core with included air-gap, individually connected in serieswith said tubes; and. a

condenser connected in series with one of said two output leads foreffecting a phase shift with respect to the other of said output leads.

2. A gaseous electric discharge tube lighting system, comprising incombination; a transfiormer having a primary winding and a secondarywinding; at least two pair of closely disposed gaseous electricdischarge tubes; and a corresponding number of pairs of parallelcircuits interconnecting said pairs of tubes with said transformersecondary winding; each of said pairs of parallel circuits including apair of reactors hav- =ing magnetic cores with included air-gaps withinductive windings respectively connected in series with thecorresponding pair of tubes, and one of each pair of parallel circuitsadditionally including a condenser in common for effecting a phasedisplacement with respect to the remaining two circuits.

3. Apparatus for operating at least four gaseous electric dischargetubes, comprising in combination; a transformer having a primary winding10 and a secondary winding: at least four individual parallel circuitsconnected with said transformer secondary winding, each of said parallelcircuits including an individual current-limiting self-inductance havinga magnetic core and an included air-gap; and a condenser in common withone half the number of said individual parallel circuits and in seriestherewith for efiecting a phase shift with respect to the other onehalf.

JOHN HEROLD BRIDGES.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,298,935 Freeman Oct. 13, 1942Re. 20,142 Boucher Oct. 27, 1936 0 1,926,423 Barclay Sept. 12, 19332,050,135 Tour Aug. 4, 1936 2,025,471 Osborne Dec. 24, 1935

